Stacked acoustic wave resonator package with laser-drilled VIAS

ABSTRACT

A packaged acoustic wave component is disclosed. The packaged acoustic wave component can include a first acoustic wave resonator that includes a first interdigital transducer electrode that is positioned over a first piezoelectric layer. The packaged acoustic wave component can also include a second acoustic wave resonator including a second interdigital transducer electrode positioned over a second piezoelectric layer. The second piezoelectric layer is bonded to the first piezoelectric layer. The packaged acoustic wave component can further include a stopper structure that is positioned over the first piezoelectric layer. The first stopper structure is positioned above a via and extends through the first piezoelectric layer. The stopper structure is in electrical communication with the first interdigital transducer electrode and includes a material which reflects at least fifty percent of light having a wavelength of 355 nanometers.

CROSS REFERENCE TO PRIORITY APPLICATION

This application claims the benefit of priority of U.S. ProvisionalPatent Application No. 62/907,255, filed Sep. 27, 2019 and titled“ACOUSTIC WAVE RESONATOR WITH LASER-DRILLED VIAS,” U.S. ProvisionalPatent Application No. 62/907,264, filed Sep. 27, 2019 and titled“METHOD OF MAKING ACOUSTIC WAVE RESONATOR WITH LASER-DRILLED VIAS,” U.S.Provisional Patent Application No. 62/907,290, filed Sep. 27, 2019 andtitled “STACKED ACOUSTIC WAVE RESONATOR PACKAGE WITH LASER-DRILLEDVIAS,” and U.S. Provisional Patent Application No. 62/907,329, filedSep. 27, 2019 and titled “METHOD OF MAKING STACKED ACOUSTIC WAVERESONATOR PACKAGE WITH LASER-DRILLED VIAS,” the disclosures of which arehereby incorporated by reference in their entirety herein.

BACKGROUND Technical Field

Embodiments of this disclosure relate to acoustic wave resonators.

Description of Related Technology

Acoustic wave filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include acoustic wave filters. An acoustic wave filtercan filter a radio frequency signal. An acoustic wave filter can be aband pass filter. A plurality of acoustic wave filters can be arrangedas a multiplexer. For example, two acoustic wave filters can be arrangedas a duplexer.

An acoustic wave filter can include a plurality of resonators arrangedto filter a radio frequency signal. Example acoustic wave filtersinclude surface acoustic wave (SAW) filters and bulk acoustic wave (BAW)filters. A surface acoustic wave resonator can include an interdigitaltransductor electrode on a piezoelectric substrate. The surface acousticwave resonator can generate a surface acoustic wave on a surface of thepiezoelectric layer on which the interdigital transductor electrode isdisposed.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

In one aspect, a packaged acoustic wave component is disclosed. Thepackaged acoustic wave component can include a first acoustic waveresonator that includes a first interdigital transducer electrode thatis positioned over a first piezoelectric layer. The Packaged acousticwave component can also include a second acoustic wave resonator thatincludes a second interdigital transducer electrode that is positionedover a second piezoelectric layer. The second piezoelectric layer isbonded to the first piezoelectric layer. The packaged acoustic wavecomponent can further include a stopper structure that is positionedover the first piezoelectric layer. The first stopper structure ispositioned above a via that extends through the first piezoelectriclayer. The stopper structure is in electrical communication with thefirst interdigital transducer electrode and includes a material whichreflects at least fifty percent of light having a wavelength of 355nanometers.

In an embodiment, the via is a laser-drilled via.

In an embodiment, the packaged acoustic wave component further includesa second stopper structure that is positioned over the firstpiezoelectric layer. The second stopper structure can be positioned overa second laser-drilled via extending through the first piezoelectriclayer. The second stopper structure can be in electrical communicationwith the second interdigital transducer electrode. The second stopperstructure can include a material which reflects at least fifty percentof light having a wavelength of 355 nanometers.

In an embodiment, the packaged acoustic wave component further includesan interconnect layer that is in electrical communication with the firstinterdigital transducer electrode and the stopper structure. Theinterconnect layer can be positioned over at least a portion of thestopper structure.

In an embodiment, the packaged acoustic wave component further includesan interconnect structure that extends between the first piezoelectriclayer and the second piezoelectric layer. The interconnect structure canbe in electrical communication with the second interdigital transducerelectrode and the second stopper structure. The interconnect structurecan be positioned over at least a portion of the second stopperstructure.

In an embodiment, the packaged acoustic wave component further includesa wall surrounding a region including the first and second acoustic waveresonators. The wall can bond the first piezoelectric layer to thesecond piezoelectric layer to form a package structure. At least one ofthe stopper structure or the second stopper structure can be locatedwithin the region surrounded by the wall.

In an embodiment, at least one of the stopper structure or secondstopper structure includes a material which reflects at leastseventy-five percent reflective of light having a wavelength of 355nanometers.

In an embodiment, at least one of the stopper structure or secondstopper structure is an aluminum layer.

In an embodiment, at least one of the stopper structure or secondstopper structure has a thickness of less than 5 micrometers.

In an embodiment, the first and second piezoelectric layers areseparated by a gap of 30 micrometers or less.

In an embodiment, an overall thickness of the packaged acoustic wavecomponent is less than 200 micrometers.

In an embodiment, the first and second piezoelectric layers are lithiumtantalate layers.

In an embodiment, the first and second piezoelectric layers are lithiumniobate layers.

In one aspect, a packaged acoustic wave component is disclosed. Thepackaged acoustic wave component can include a first acoustic waveresonator that includes a first interdigital transducer electrode thatis positioned over a first piezoelectric layer. The packaged acousticwave component can also include a second acoustic wave resonator thatincludes a second interdigital transducer electrode that is positionedover a second piezoelectric layer. The second piezoelectric layer isbonded to the first piezoelectric to form a package that encapsulatesthe first and second interdigital transducer electrodes. The packagedacoustic wave component can further include a stopper structure that ispositioned over the first piezoelectric layer. The stopper structurethat is positioned over a via that extends through the firstpiezoelectric layer. The stopper structure includes aluminum.

In an embodiment, the via is a laser-drilled via.

In an embodiment, the packaged acoustic wave component further includesa first conductive structure that extends into the via. The firstconductive structure can be in electrical communication with the firstinterdigital transducer electrode.

In an embodiment, the packaged acoustic wave component further includesa second stopper structure that is positioned over the firstpiezoelectric layer. The second stopper structure can be positioned overa second laser-drilled via that extends through the first piezoelectriclayer. The stopper structure and second stopper structure can includealuminum. The packaged acoustic wave component can further include asecond conductive structure that extends into the second via. The secondconductive structure can be in electrical communication with the secondinterdigital transducer electrode. The packaged acoustic wave componentcan further includes an interconnect structure that extends between thefirst piezoelectric layer and the second piezoelectric layer. Theinterconnect structure can be in electrical communication with thesecond interdigital transducer electrode and the second stopperstructure. The interconnect structure can be positioned over at least aportion of the second stopper structure.

In an embodiment, the packaged acoustic wave component further includesan interconnect layer that is in electrical communication with the firstinterdigital transducer electrode and the stopper structure. Theinterconnect layer can be positioned over at least a portion of thestopper structure.

In an embodiment, the packaged acoustic wave component further includesa wall that bonds a region that includes the first and second acousticwave resonators. The wall can also bond the first piezoelectric layer tothe second piezoelectric layer to form a package.

In an embodiment, the stopper structure has a thickness of less than 5micrometers.

In an embodiment, the first and second piezoelectric layers areseparated by a gap of 30 micrometers or less.

In an embodiment, an overall thickness of the package is less than 200micrometers.

In an embodiment, the first acoustic wave resonator is associated with afirst frequency band, and the second acoustic wave resonator isassociated with a second frequency band. The first frequency band can bedifferent than the second frequency band.

In an embodiment, a duplexer comprising the packaged acoustic wavecomponent disclosed herein.

In one aspect, a method of fabricating a packaged acoustic wavecomponent is disclosed. The method can include providing a firstacoustic wave resonator that include a first interdigital transducerelectrode on a first piezoelectric layer. The first piezoelectric layersupports a stopper structure that includes a material which reflects atleast fifty percent of light that has a wavelength of 355 micrometers.The method can also include providing a second acoustic wave resonatorthat includes a second interdigital transducer electrode positioned on asecond piezoelectric layer. The method can further include bonding thefirst piezoelectric layer to the second piezoelectric layer to form apackage structure that encapsulates the first and second interdigitaltransducer electrodes. The method can further include forming a via byapplying laser light to an outside surface of the first piezoelectriclayer at a location opposite the stopper structure. The via extendsthrough the first piezoelectric layer and exposing a portion of thestopper structure.

In an embodiment, the first piezoelectric layer further supports asecond stopper structure including a material which reflects at leastfifty percent of light having a wavelength of 355 micrometers.

In an embodiment, the method further includes applying laser light tothe outside surface of the second piezoelectric layer at a locationopposite the second stopper structure to form a second laser-drilled viaextending through the first piezoelectric layer and exposing a portionof the second stopper structure. The first piezoelectric layer canfurther support an interconnect structure in contact with the secondstopper structure, and the second stopper structure is located betweenthe interconnect structure and the first piezoelectric layer. The methodcan further include forming a first conductive structure that extendsinto the via and in contact with the stopper structure and a secondconductive structure that extends into the second via and in contactwith the second stopper structure. Bonding the first piezoelectric layerto the second piezoelectric layer can include bonding an upper surfaceof the interconnect structure to an interconnect bond pad that ispositioned over the second piezoelectric layer and in electricalcommunication with the second interdigital transducer electrode.

In an embodiment, the first piezoelectric layer further supports aninterconnect layer that is in electrical communication with the firstinterdigital transducer electrode and the stopper structure. The stopperstructure can be located between the first piezoelectric layer and theinterconnect layer.

In an embodiment, the first piezoelectric layer further supports a wallstructure surrounding the first acoustic wave resonator and the stopperstructure in a plan view. Bonding the first piezoelectric layer to thesecond piezoelectric layer can include bonding an upper surface of thewall structure to a wall bond pad that is positioned over the secondpiezoelectric layer and surrounding the second acoustic wave resonator.

In an embodiment, the first acoustic wave resonator is associated with afirst frequency band and wherein the second acoustic wave resonator isassociated with a second frequency band. The first frequency band can bedifferent than the second frequency band.

In one aspect, a method of fabricating a packaged acoustic wavecomponent is disclosed. The method can include providing a firstacoustic wave resonator component that includes a first piezoelectriclayer. The first piezoelectric layer supports a stopper structure and afirst interdigital transducer electrode. The stopper structure includingaluminum. The method can also include providing a second acoustic waveresonator component that includes a second piezoelectric layer thatsupports a second interdigital transducer electrode. The method canfurther include bonding the first piezoelectric layer to the secondpiezoelectric layer to form a package encapsulating the first and secondinterdigital transducer electrodes. The can method further includeforming a via by applying laser light to an outside surface of the firstpiezoelectric layer at a location opposite the stopper structure. Thevia extends through the first piezoelectric layer and exposes a portionof the stopper structure.

In an embodiment, the first piezoelectric layer further supports asecond stopper structure including aluminum. The method can furtherinclude applying laser light to the outside surface of the secondpiezoelectric layer at a location opposite the second stopper structureto form a second laser-drilled via that extends through the firstpiezoelectric layer and exposes a portion of the second stopperstructure. The first piezoelectric layer can further support aninterconnect structure that is in contact with the second stopperstructure. The second stopper structure can be located between theinterconnect structure and the first piezoelectric layer. Bonding thefirst piezoelectric layer to the second piezoelectric layer can comprisebonding an upper surface of the interconnect structure to aninterconnect bond pad that is positioned over the second piezoelectriclayer and in electrical communication with the second interdigitaltransducer electrode.

In an embodiment, the method further includes forming a first conductivestructure that extends into the via and in contact with the stopperstructure.

In an embodiment, the first acoustic wave resonator is associated with afirst frequency band, and the second acoustic wave resonator isassociated with a second frequency band. The first frequency band isdifferent than the second frequency band.

In an embodiment, the first and second piezoelectric layers are lithiumtantalate layers.

In an embodiment, the first and second piezoelectric layers are lithiumniobate layers.

In one aspect, an acoustic wave component is disclosed. The acousticwave component can include a piezoelectric layer, an interdigitaltransducer electrode positioned over the piezoelectric layer, a stopperstructure that is in electrical communication with the interdigitaltransducer electrode, and a via extending through the piezoelectriclayer to the stopper structure. The stopper structure includes amaterial which reflects at least fifty percent of light having awavelength of 355 nanometers.

In an embodiment, the stopper structure includes a material whichreflects at least seventy-five percent of light having a wavelength of355 nanometers.

In an embodiment, the stopper structure is an aluminum layer.

In an embodiment, the stopper structure has a thickness of less than 15micrometers. The stopper structure can have a thickness of less than 5micrometers. The stopper structure can have a thickness of more than 1micrometer.

In an embodiment, a thickness of the stopper structure is less thantwenty-two percent of a thickness of the piezoelectric layer. Thethickness of the stopper structure can be less than four percent of thethickness of the piezoelectric layer. The thickness of the stopperstructure can be at least one percent of the thickness of thepiezoelectric layer.

In an embodiment, the via is laser-drilled.

In an embodiment, the via has a frustoconical shape.

In an embodiment, the acoustic wave component further includes aninterconnect layer that is in electrical communication with theinterdigital transducer electrode and the stopper structure. The stopperstructure can be located between the piezoelectric layer and a portionof the interconnect layer. The interconnect layer can be a copper layer.

In an embodiment, the acoustic wave component further includes aconductive structure that extends into the via and in electricalcommunication with the stopper structure.

In an embodiment, the piezoelectric layer is a lithium tantalate layer.

In an embodiment, the piezoelectric layer is a lithium niobate layer.

In one aspect, an acoustic wave component is disclosed. the acousticwave component can include a piezoelectric layer, an interdigitaltransducer electrode positioned over a first surface of thepiezoelectric layer, a stopper structure positioned over the firstsurface of the piezoelectric layer and in electrical communication withthe interdigital transducer electrode, a via that extends through aportion of the piezoelectric substrate that is covered by the stopperstructure, and a conductive structure that extends into the via and incontact with the stopper structure. The stopper structure includesaluminum.

In an embodiment, the via is a laser-drilled via.

In an embodiment, the conductive structure extends over at least aportion of a second surface of the piezoelectric layer opposite thefirst surface of the piezoelectric layer.

In an embodiment, the acoustic wave component further includes aninterconnect layer that is in electrical communication with theinterdigital transducer electrode and the stopper structure. The stopperstructure can be located between the piezoelectric layer and theinterconnect layer.

In an embodiment, a thickness of the stopper structure is less than fourpercent of a thickness of the piezoelectric layer.

In an embodiment, the stopper structure has a thickness of less than 5micrometers.

In an embodiment, the piezoelectric layer is a lithium tantalate layer.

In an embodiment, the piezoelectric layer is a lithium niobate layer.

In one aspect, a method of fabricating an acoustic wave component isdisclosed. The method can include forming a stopper structure over apiezoelectric layer. The stopper structure includes a material whichreflects at least fifty percent of light having a wavelength of 355nanometers. The method can also include forming an interdigitaltransducer electrode over the piezoelectric layer. The interdigitaltransducer layer is electrically connected to the stopper structure. Themethod can further include forming a via by applying laser light to thepiezoelectric layer on a side of the piezoelectric layer opposite thestopper structure. The via extends through the piezoelectric layer andexposes a portion of the stopper structure.

In an embodiment, the method further includes forming a conductivestructure that extends into the via and in contact with the stopperstructure.

In an embodiment, the method further includes forming an interconnectstructure that is in electrical communication with the stopper structureand the interdigital transducer electrode. At least a portion of theinterconnect structure can extend over the stopper structure.

In an embodiment, the stopper structure includes a material whichreflects at least seventy-five percent of light having a wavelength of355 nanometers.

In an embodiment, the stopper structure is an aluminum layer.

In an embodiment, the stopper structure has a thickness of less than 5micrometers.

In an embodiment, the method further includes using an endpoint detectorwhile applying laser light to the piezoelectric layer to detect exposureof the stopper structure to the etching laser.

In an embodiment, the piezoelectric layer is a lithium tantalate layer.

In an embodiment, the piezoelectric layer is a lithium niobate layer.

In one aspect, a method of fabricating an acoustic wave component isdisclosed. The method can include forming a stopper structure over apiezoelectric layer. The stopper structure includes aluminum. The methodcan also include forming an interdigital transducer electrode over thepiezoelectric layer. The interdigital transducer electrode iselectrically connected to the stopper structure. The method can furtherinclude forming a via by applying laser light to the piezoelectric layeron a side of the piezoelectric layer opposite the stopper structure. Thevia extends through the piezoelectric layer and exposes a portion of thestopper structure.

In an embodiment, the method further includes forming a conductivestructure that extends into the via and in contact with the stopperstructure.

In an embodiment, the method further comprises forming an interconnectstructure that is in electrical communication with the stopper structureand the interdigital transducer electrode. At least a portion of theinterconnect structure can extend over the stopper structure.

In an embodiment, the method further includes using an endpoint detectorwhile applying laser light to the piezoelectric layer to detect exposureof the stopper structure to the etching layer.

In an embodiment, the stopper structure has a thickness of less than 5micrometers.

In one aspect, a method of fabricating an acoustic wave component isdisclosed. The method can include providing a piezoelectric layer withan interdigital transducer electrode and a stopper structure on a firstside of the piezoelectric layer. The stopper structure includes amaterial which reflects at least fifty percent of light having awavelength of 355 nanometers. The method can also include applying laserlight to a second side of a piezoelectric layer opposite to the firstside of the piezoelectric layer to form a via through the piezoelectriclayer. The via extends through the piezoelectric layer to the stopperstructure.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment. Thus, theinnovations may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIGS. 1A and 1B illustrates a cross section of a surface acoustic wave(SAW) resonator component at various stages of a manufacturing process.

FIG. 2 illustrates a perspective view of a packaged acoustic wavecomponent including a first surface acoustic wave resonator componentpositioned over a first wafer and a second surface acoustic waveresonator component positioned over a second wafer.

FIG. 3 illustrates a cross section of a packaged acoustic wave componentsuch as the packaged acoustic wave component of FIG. 2 .

FIG. 4A is a cross section schematically illustrating the response of amaterial to impingement of a laser.

FIG. 4B is a graph showing the reflection ratios of various metals as afunction of wavelength.

FIG. 5A is a top plan view schematically illustrating the footprint of asingle surface acoustic wave resonator component.

FIG. 5B is a top plan view schematically illustrating the footprint of apackaged acoustic wave component including a pair of stacked resonators.

FIGS. 6A to 6E illustrate cross-sections of a portion of a surfaceacoustic wave resonator component at various stages of a manufacturingprocess according to an embodiment.

FIGS. 7A to 7O illustrate cross-sections of a packaged acoustic wavecomponent including first and second surface acoustic wave resonatorcomponents at various stages of a manufacturing process according to anembodiment.

FIG. 8 is a schematic diagram of a transmit filter that includes asurface acoustic wave resonator according to an embodiment.

FIG. 9 is a schematic diagram of a receive filter that includes asurface acoustic wave resonator according to an embodiment.

FIG. 10 is a schematic diagram of a radio frequency module that includesa surface acoustic wave component according to an embodiment.

FIG. 11 is a schematic diagram of a radio frequency module that includesduplexers with surface acoustic wave resonators according to anembodiment.

FIG. 12 is a schematic block diagram of a module that includes a poweramplifier, a radio frequency switch, and duplexers that include one ormore surface acoustic wave resonators according to an embodiment.

FIG. 13 is a schematic block diagram of a module that includes anantenna switch and duplexers that include one or more surface acousticwave resonators according to an embodiment.

FIG. 14 is a schematic block diagram of a wireless communication devicethat includes a filter in accordance with one or more embodiments.

FIG. 15 is a schematic block diagram of another wireless communicationdevice that includes a filter in accordance with one or moreembodiments.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following description of certain embodiments presents variousdescriptions of specific embodiments. However, the innovations describedherein can be embodied in a multitude of different ways, for example, asdefined and covered by the claims. In this description, reference ismade to the drawings where like reference numerals can indicateidentical or functionally similar elements. It will be understood thatelements illustrated in the figures are not necessarily drawn to scale.Moreover, it will be understood that certain embodiments can includemore elements than illustrated in a drawing and/or a subset of theelements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

Acoustic wave filters can filter radio frequency (RF) signals in avariety of applications, such as in an RF front end of a mobile phone.An acoustic wave filter can be implemented with surface acoustic wave(SAW) resonators.

A manufacturing process of a resonator device can include a laserdrilling process to form one or more vias in a substrate, such as apiezoelectric substrate, after the formation of resonator structures onthe opposite side of the substrate. The via can allow electricalconnections to be formed with interdigital transducer (IDT) electrodes.In some embodiments, the vias allow connections to be made with IDTelectrodes in the interior of a package formed by a pair of stackedresonators.

A stopper layer or stopper structure can be utilized on the oppositeside of the piezoelectric substrate to be laser drilled. While a copperIDT electrode or a copper interconnect layer in electrical communicationwith an IDT electrode can be used as a stopper structure, the percentageof laser light absorbed by the copper layer can be substantial. Theportions of the copper layer initially exposed by the etching layer canbe exposed to a substantial number of additional laser pulses as theremainder of the via is drilled, to achieve its final state. Theformation of a sufficiently thick interconnect layer in the region inwhich the laser via is to be formed can involve the use of expensivedeposition techniques, and can affect the thickness of a package formedby a stacked pair of resonators.

Aspects of this disclosure relate to the use of a stopper structurewhich is highly reflective to the light used in the laser etchingprocess. For example, a stopper layer of aluminum can be used which isroughly six times thinner than a stopper layer made of copper. Thestopper structure may be located between the piezoelectric substrate andan interconnect layer including a different material, such as copper.The overall thickness of such a layer stack can be less than thethickness of a comparatively effective stopper layer formed entirely ofcopper. Because the interconnect layer may not serve as a stopperstructure, the interconnect layer can be made thinner, and may be formedusing a wider variety of deposition techniques.

FIG. 1A illustrates a cross section of a surface acoustic wave resonatorcomponent at a stage of a manufacturing process. The manufacturingprocess may include a laser etching process. The illustrated SAWresonator component 100 in FIG. 1A includes a piezoelectric layer 110and an interconnect layer 122 positioned over a first surface thepiezoelectric layer 110. The second surface of the piezoelectric layer110, opposite the interconnect layer 122, is exposed to illumination 190from an etching laser. In some embodiments, the piezoelectric layer 110may include a material such as lithium tantalite (LT) or lithium niobate(LN), and the etching layer may emit light at a wavelength of 355nanometers (nm), suitable for laser etching of a lithium-includingpiezoelectric substrate. The interconnect layer 122 may be in electricalcommunication with an IDT electrode (not shown in FIG. 1A), and on thesame side of the piezoelectric layer 110 as the interconnect layer.

FIG. 1B illustrates a cross section of the surface acoustic waveresonator component of FIG. 1A at a later stage of a manufacturingprocess. Laser light has been applied to the piezoelectric layer 110,and the laser has ablated a portion of the piezoelectric layer 110 toform a laser-drilled via 180 extending through the piezoelectric layer110 and exposing a portion of the interconnect layer 122. Thelaser-drilled via 180 may have a frustoconical shape, with a widercross-sectional dimension 182 at the opening of the via 112, and anarrower cross-sectional dimension 184 at the base of the via 180,adjacent the interconnect layer 122, such that the via 180 has angledsidewalls 186.

Because of exposure to the laser illumination 190, a section 124 of theinterconnect layer 122 has been ablated, melted, or otherwise affectedby exposure to the laser pulses, such that the laser-drilled via 180extends into the interconnect layer 122. Although described as a section124 of the interconnect layer 122 the section 124 may in someembodiments be a portion of an IDT electrode itself. In someembodiments, the laser etching process may be monitored using anendpoint detector to detect plasma generated by ablation of thelithium-containing piezoelectric layer. When the plasma generationtapers off, the laser etching process may be stopped. However, there maybe as many as 20 or 30 additional laser pulses emitted between the pointat which the interconnect layer 122 is first exposed and the point atwhich the via 180 has been fully etched.

The interconnect layer 122 may not be directly in contact with thepiezoelectric layer 110 in the area overlying the via 180. In variousembodiments, additional layers not specifically illustrated in FIGS. 1Aand 1B may be disposed between the interconnect layer 122 and thepiezoelectric layer 110. Depending on the thickness and composition ofthese layers, such layers may have minimal effect on the laser-etchingprocess.

In some embodiments, the overall height of a SAW resonator may beconstrained by various design considerations. For example, SAWresonators may be provided in a stacked arrangement, with a first SAWresonator positioned over a first surface of a first piezoelectricsubstrate, and a second SAW resonator positioned over a first surface ofa second piezoelectric substrate, with the first surfaces of the firstand second substrates facing one another.

FIG. 2 illustrates a perspective view of a packaged acoustic wavecomponent 200 including a first surface acoustic wave resonatorcomponent positioned over a first wafer and a second surface acousticwave resonator component positioned over a second wafer. The first SAWresonator component 220 a positioned over the lower piezoelectric wafer210 a may be associated with a first frequency band, and the second SAWresonator component 200 b positioned over the upper piezoelectric wafer210 b may be associated with a second frequency band. Each of the SAWresonator components 200 a and 200 b can include any suitable number ofSAW resonators. The packaged acoustic wave component 200 (e.g., stackedresonator structure) may be configured to operate as a duplexer, withone of the first SAW resonator component 220 a or the second SAWresonator component 220 b configured to operate as a receive filter, andthe other configured to operate as a transmit filter.

The lower piezoelectric wafer 210 a may be wafer bonded to the upperpiezoelectric wafer 210 b using any suitable wafer bonding technique,for example, as discussed in greater detail below. The lowerpiezoelectric wafer 210 a and the upper piezoelectric wafer 210 b mayform a package enclosing the IDT electrodes of SAW resonator component220 a and the second SAW resonator component 220 b.

FIG. 3 illustrates a cross section of a packaged acoustic wave componentsuch as the packaged acoustic wave component of FIG. 2 . The upperpiezoelectric wafer 210 b has a thickness of h_(b), the lowerpiezoelectric wafer 210 a has a thickness of h_(a), and there is a gap202 of thickness h_(g) between the upper piezoelectric wafer 210 b andthe lower piezoelectric wafer 210 a. The package has an overallthickness of h, where h is given by the sum of h_(a), h_(b), and h_(g).

Vias 280 extend through at least one of the upper piezoelectric wafer210 b and the lower piezoelectric wafer 210 a, allowing electricalconnections to be made with the IDT electrodes of the first SAWresonator component 220 a and/or the second SAW resonator component 220b. In the illustrated embodiment, the upper piezoelectric wafer 210 b isthicker than the lower piezoelectric wafer 210 a. In such an embodiment,the vias 280 may be formed in the thinner lower piezoelectric wafer 210a, to facilitate formation of the vias 280 without etching through theadditional thickness of the upper piezoelectric wafer 210 b.

In the illustrated embodiment, certain of the vias 280 are in electricalconnection with the IDT electrodes of the first SAW resonator component220 a or with a conductive structure 224 in electrical communicationwith the IDT electrodes of the first SAW resonator component 220 a.Other of the vias 280 are in electrical connection with the IDTelectrodes of the second SAW resonator component 220 b via a conductivestructure 226 extending between the lower and upper piezoelectric wafers210 a and 210 b. The conductive structure 226 may be a layer ofconductive material or a stack of layers of conductive material. In someembodiments, the conductive structure 226 may be formed by bonding aconductive structure positioned over the upper piezoelectric wafer 210 bto a conductive structure positioned over the lower piezoelectric wafer210 a.

The conductive structures 224 and 226 serve as stopper structures forthe laser etching of the vias 280, and are of sufficient thickness towithstand the laser etching process while the vias 280 are being formed.In an embodiment in which the vias 280 are formed after the upperpiezoelectric wafer 210 b is bonded to the lower piezoelectric wafer 210a to form a package, the conductive structures 224 and 226 are ofsufficient thickness that the laser does not pierce the conductivestructure 224 and 226 and expose portions of the upper piezoelectricwafer 210 b or the second SAW resonator component 220 b to the etchinglaser.

The thickness of the conductive structures 224 and 226 c can constrainthe minimum thickness h_(g) of the gap 202, and thereby constrain aminimum overall thickness h of the package. The thickness of theconductive structures 224 and 226 may be dependent on a number offactors, one of which is the composition of the conductive structures224 and 226.

FIG. 4A is a cross section schematically illustrating the response of amaterial to impingement of a laser. The material 300 is exposed toillumination 390 from an etching laser. In some embodiments, theillumination 390 from the etching layer may be a series of discretepulses. A portion of the illumination 390 incident upon the material 300is reflected as reflected radiation 392. The reflected radiation 392 maybe scattered over a range of angles, due in part to the surfaceconditions of the material 300 and the composition of the material 300.Another portion of the illumination 390 may be transmitted through thematerial as transmitted illumination 394. Another portion of theillumination 390 may be absorbed by the material 300 as absorbedradiation 396.

All of the illumination 390 incident upon the material 300 should beeither absorbed as absorbed radiation 396, transmitted as transmittedillumination 394, or reflected as reflected radiation 392. Therespective percentages of illumination 390 absorbed as absorbedradiation 396, transmitted as transmitted illumination 394, andreflected as reflected radiation 392 should therefore add to 100%. Formetallic materials of sufficient thickness, no radiation should betransmitted through the material 300, and all of the incident laserlight will either be absorbed as absorbed radiation 396 or reflected asreflected radiation 392. The reflectivity of the material 300 to a givensource of illumination 390 will therefore be directly related to theamount of illumination 390 absorbed by the material 300.

FIG. 4B is a graph showing the reflection ratios of various metals as afunction of wavelength. Curve 410 illustrates the reflection ratio ofcopper (Cu) as a function of wavelength. In particular, at 355 nm, thereflectivity of copper is roughly 35%. As a sufficiently thick layer ofcopper will not transmit light therethrough, nearly two-thirds of lightemitted at 355 nm will be absorbed by the copper layer. The use ofcopper as a stopper layer for a 355 nm etching laser can involve a layerwhich is thicker than the other metals shown in the graph of FIG. 4B, asa substantial amount of energy from the laser will be absorbed by acopper stopper layer once the underlying layer has been etched to exposea portion of the copper stopper layer. This absorption of laser energywill result in melting or ablation of the stopper layer

Curves 420 and 430 illustrate the reflection ratios of iron (Fe) andgold (Au) as functions of wavelength. Both iron and gold have areflectivity of roughly 50% at 355 nm. The absorption rate of iron orgold is roughly 75% of the absorption rate of copper. The use of iron orgold as a stopper layer allows the use of a stopper layer which isroughly 25% thinner than a comparatively effective copper layer.

Curve 440 illustrates the reflection ratio of silver (Ag) as a functionof wavelength. The reflectivity of silver at 355 nm is roughly 75%, andthe absorption rate of silver at that wavelength is roughly 38% that ofthe absorption rate of copper. A silver layer used as a stopper layermay be more than 61% thinner than a comparably effective copper layer.

Curve 440 illustrates the reflection ratio of silver (Ag) as a functionof wavelength. The reflectivity of silver at 355 nm is roughly 75%, andthe absorption rate of silver at that wavelength is roughly 38% that ofthe absorption rate of copper. A silver layer used as a stopper layermay be more than 61% thinner than a comparably effective copper layer.

Curve 450 illustrates the reflection ratio of aluminum (Al) as afunction of wavelength. While silver is more reflective than aluminum inthe visible wavelengths, the reflectivity of aluminum remains high forshorter wavelengths in the near-visible range, while the reflectivity ofsilver drops below that of aluminum. For light having a wavelength of355 nm, the reflectivity of aluminum is roughly 90%, and the absorptionrate of aluminum at that wavelength is roughly 15.4% that of copper. Analuminum layer can therefore be 84.6% thinner than a copper stopperlayer, while providing equivalent protection for a 355 nm etching laser.

By utilizing an aluminum stopper layer, the thickness of the stopperlayer may be reduced by almost an order of magnitude. In a package suchas the package of FIGS. 2 and 3 , the thickness of the stopper layer maybe a controlling factor in minimizing the thickness h_(g) of the gap 202between the upper piezoelectric wafer 210 b and the lower piezoelectricwafer 210 a. The thickness h_(g) of the gap 202, in turn, can be acontrolling factor in the overall thickness of the package. If one ofthe wafers is roughly 70 micrometers (um) in thickness, and the other ofthe wafers is roughly 100 um in thickness, an overall package thicknessof 200 um can be provided if the thickness h_(g) of the gap 202 is lessthan 30 um.

In some embodiments, the overall footprint of a packaged acoustic wavecomponent including stacked resonators can be less than the footprint oftwo resonators side-by-side on a single substrate. Because ofmodifications to the design of the resonators to accommodate, forexample, interconnections between the lower wafer and the upper wafer,FIG. 5A shows that a footprint 520 a of a single surface acoustic waveresonator component extends beyond the boundaries of the functional area510 a of the resonator component by a distance 522 a. Although thefunctional area 510 a of the resonator component is schematicallydepicted as being centered within the footprint 520 a, the actualpositioning of the functional area 510 a of the resonator componentwithin the footprint 520 a may vary depending on the design of theresonator component.

In contrast, FIG. 5B shows that the footprint 520 b of a resonatorcomponent of a packaged acoustic wave component including a stackedresonator design is larger than the footprint 520 a of FIG. 5A. Inaddition, it can be seen that the footprint 520 b may be wider in alateral direction than in a longitudinal direction. The footprint 520 bof the resonator component extends beyond the boundaries of thefunctional area 510 b of the larger of the resonator components by adistance 522 b in a lateral direction, and in by distance 522 c in alongitudinal direction. In an embodiment in which the lateral distance522 b is longer than the longitudinal distance 522 c, the additionallength may be due to the placement of vias extending through one of thesubstrates and allowing electrical communication with each of theresonator components in the stacked resonator package. In embodiments inwhich the vias are formed in only one of the two substrates, aconductive pillar may extend between the two substrates of the package,allowing electrical communication with the resonator componentpositioned over the upper substrate through a via formed through thelower substrate. A package wall sealing the first substrate to thesecond substrate will also increase the size of the footprint 520 b.

As discussed above with respect to the resonator of FIG. 5A, althoughthe functional area 510 b of the resonator component of FIG. 5B isschematically depicted as being centered within the footprint 520 b, theactual positioning of the functional area 510 b of the resonatorcomponent within the footprint 520 b may vary depending on the design ofthe resonator component. For example, a via providing electricalcommunication with the upper resonator component may be on the oppositeside of the lower resonator component as a via providing electricalcommunication with the lower resonator component, or both vias may be onthe same side of the lower resonator component.

Despite the additional size of the footprint 520 b, the stackedresonator arrangement of the packaged acoustic wave component allows theoverall footprint 520 b of two resonator components to be smaller thanthe total footprint of two resonator component footprints 520 aside-by-side. The total reduction in size will vary depending on therelative size of the functional area 510 b relative to the componentsformed in the remainder of the footprint. In some embodiments, areduction of at least 35% can be achieved via a stacked resonatorarrangement. In other embodiments, a reduction of almost 45% or more canbe achieved via a stacked resonator arrangement.

While the footprint of the packaged acoustic wave component includingstacked resonators can be reduced in comparison to a side-by-sidearrangement of two resonator components, the height of the stackedresonator components is increased. Depending on the amount of heightincrease, this height increase may make a stacked arrangement unsuitablefor certain implementations. If the stacked packaged acoustic wavecomponent can be made sufficiently thin, the stacked packaged acousticwave component can be used in place of a pair of side-by-side resonatorcomponents in certain implementations. For example, some implementationsmay desire a package thickness of less than 200 um.

If a copper stopper structure is used when forming laser-drilled vias,the space for the thick copper stopper structure may make achieving sucha package impractical or impossible. By using a stopper structure whichis more reflective to the illumination from a 355 nm etching laser, thespecified spacing between the package substrates may be reduced. If asufficiently reflective material is used as the stopper structure, thespecified spacing between the package substrates may become a functionof resonator dimensions or other package components, rather than stopperstructure dimensions.

FIGS. 6A-6E illustrate cross sections of a surface acoustic waveresonator component at various stages of a manufacturing process. Themanufacturing process may include a laser etching process. Theillustrated SAW resonator component 600 in FIG. 6A includes apiezoelectric layer 610 and an interconnect layer 622 positioned over afirst surface the piezoelectric layer 610. The interconnect layer 622may be in electrical communication with an IDT electrode (not shown inFIG. 6A) and on the same side of the piezoelectric layer 610 as theinterconnect layer 622.

The SAW resonator component 600 of FIG. 6A differs from the SAWresonator component 100 of FIG. 1A in that the interconnect layer 622includes a stopper layer 628 located between the interconnect layer 622and the piezoelectric layer 610 in at least one section of theinterconnect layer 622. In some embodiments, the stopper layer includesa material which is at least 50% reflective to illumination at awavelength of 355 nm. In some of these embodiments, the stopper layerincludes a material which is at least 75% reflective to illumination ata wavelength of 355 nm. In certain embodiments, the stopper layer 628includes aluminum.

By using a stopper layer 628 that is relatively highly reflective oflaser light (e.g., an aluminum stopper layer), the stopper layer 628 canbe relatively thin compared to a less reflective stopper layer (e.g., acopper stopper layer). For example, the stopper layer 628 can have athickness of less than 15 micrometers. In some instances, the stopperlayer 628 can have a thickness of less than 5 micrometers. In someinstances, the stopper layer 628 can have a thickness of less than 3micrometers. The stopper layer 628 can have a thickness in a range from1 micrometer to 15 micrometers, such as in a range from 1 micrometer to5 micrometers. The stopper layer 628 can have a thickness that is lessthan about 25% of a thickness of the piezoelectric layer 610, such asless than 22% of the thickness of the piezoelectric layer 610. In someinstances, the thickness of the stopper layer 628 is less than 4% of thethickness of the piezoelectric layer 610.

The second surface of the piezoelectric layer 610, opposite theinterconnect layer 622 and in the region of the stopper layer 628, isexposed to illumination 690 from an etching laser. As previouslydiscussed, the piezoelectric layer 610 may include a material such aslithium tantalite (LT) or lithium niobate (LN), and the etching layermay emit light at a wavelength of 355 nm, suitable for laser etching ofa lithium-including piezoelectric substrate.

FIG. 6B illustrates a cross section of the surface acoustic waveresonator component of FIG. 6A at a later stage of a manufacturingprocess. The etching laser has ablated a portion of the piezoelectriclayer 610 to form a laser-drilled via 680 extending through thepiezoelectric layer 610 and into a portion of the stopper layer 628.However, the stopper layer 628 has prevented the via from extending intothe overlying interconnect layer 622. The laser-drilled via 680 has agenerally frustoconical shape, with a wider cross-sectional dimension681 at the opening of the via 680, and a narrower cross-sectionaldimension 683 at the base of the via 680, adjacent the interconnectlayer 622, such that the via 680 has angled sidewalls 685.

Because of exposure to the laser illumination 190, a section of thestopper layer 628 has been ablated, melted, or otherwise affected byexposure to the laser pulses, such that the laser-drilled via 680extends into the stopper layer 628. Although the stopper layer 628 isdepicted as underlying a section of the interconnect layer 622 thestopper layer 628 may in some embodiments underlie a portion of an IDTelectrode itself.

As previously discussed, the laser etching process may be monitoredusing an endpoint detector to detect plasma generated by ablation of thelithium-containing piezoelectric layer. When the plasma generationtapers off, the laser etching process can be stopped. However, there maybe as many as 20 or 30 additional laser pulses emitted between the pointat which the stopper layer 628 is first exposed and the point at whichthe via 680 has been fully etched.

The stopper layer 628 may not be directly in contact with thepiezoelectric layer 610 in the area overlying the via 680. In variousembodiments, additional layers not specifically illustrated in FIGS. 6Aand 6B may be disposed between the stopper layer 628 and thepiezoelectric layer 610. Depending on the thickness and composition ofthese layers, such layers may have minimal effect on the laser-etchingprocess.

In FIG. 6C, it can be seen that a seed layer 682 has been sputterdeposited on the side of the piezoelectric layer 610 opposite theinterconnect layer 622 and the stopper layer 628. In addition, aphotoresist layer 684 has been formed over the seed layer 682, andpatterned to expose a portion of the seed layer 682 covering theinterior of the via 680.

In FIG. 6D, it can be seen that an interconnect structure 686 has beenformed over the exposed portion of the seed layer 682, such that theinterconnect structure 686 covers at least the via 680 and the portionof the seed layer 682 immediately surrounding the via 680. Theinterconnect structure 686 may be formed, for example, by electroplatingonto the seed layer 682. The interconnect structure 686 may includecopper or other suitable conductive materials. The interconnectstructure 686 may include multiple layers of materials, such as a layerof copper followed by a layer of tin.

In FIG. 6E, the photoresist layer 684 and the seed layer 682 have beenremoved, leaving the interconnect structure 686. The interconnectstructure 686 extends into the via 680, and is in electricalcommunication with the interconnect layer 622 on the opposite side ofthe piezoelectric layer 610, allowing communication through thepiezoelectric layer.

Similar processes can be used as part of a fabrication process for apackaged acoustic wave component with a stacked resonator arrangement.FIGS. 7A to 7K illustrate cross sections of a packaged acoustic wavecomponent at various stages of a manufacturing process. In FIG. 7A, asurface acoustic wave (SAW) resonator wafer 700 a is provided, includinga piezoelectric layer 710 a having a plurality of IDT electrodes 720 aformed thereon. In some embodiments, the piezoelectric layer 710 mayinclude any suitable piezoelectric material such as a lithium niobate(LN) layer or a lithium tantalate (LT) layer. As will be described ingreater detail below, the thickness of the piezoelectric layer 710 a inthe provided SAW wafer 700 a may not correspond to the final thicknessof the piezoelectric layer 710 a in the final SAW package. In addition,stopper structures 728 a and 728 b have been formed on portions of thepiezoelectric layer 710 a adjacent the plurality of IDT electrodes 720a. Additional structures not depicted in FIG. 7A may also be formed,including electrodes in electrical communication with the plurality ofIDT electrodes 720 a. Such electrodes may include aluminum, and may bethicker than the plurality of IDT electrodes 720 a.

In some embodiments, the stopper structures 728 a and 728 b each includea material which is at least 50% reflective to illumination at awavelength of 355 nm. In some of these embodiments, the stopperstructures 728 a and 728 b each include a material which is at least 75%reflective to illumination at a wavelength of 355 nm. In certainembodiments, the stopper structures 728 a and 728 b each includealuminum.

By using stopper structures 728 a and 728 b that are relatively highlyreflective of laser light (e.g., aluminum stopper structures), thestopper structures 728 a and 728 b can be relatively thin compared toless reflective stopper structures (e.g., copper stopper structures).For example, the stopper structures 728 a and 728 b can each have athickness of less than 15 micrometers. In some instances, the stopperstructures 728 a and 728 b can each have a thickness of less than 5micrometers. In some instances, the stopper structures 728 a and 728 bcan each have a thickness of less than 3 micrometers. The stopperstructures 728 a and 728 b can each have a thickness in a range from 1micrometer to 15 micrometers, such as in a range from 1 micrometer to 3micrometers. The stopper structure 728 a can have a thickness that isless than about 25% of a thickness of the piezoelectric layer 710 a,such as less than 22% of the thickness of the piezoelectric layer 710 a.In some instances, the thickness of the stopper structure 728 a is lessthan 4% of the thickness of the piezoelectric layer 710 a.

In FIG. 7B, a first photoresist layer has been deposited over the SAWwafer 700 a, and patterned via photolithography to leave a firstphotoresist layer 730 extending over the IDT electrodes 720 a andstopper structures 728 a and 728 b, and including apertures 732 a and732 b adjacent the IDT electrode layers and overlying the stopperstructures 728 a and 728 b. The apertures 732 a and 732 b in the firstphotoresist layer 730 will be used in part to define the locations ofstop structures under which laser-drilled vias can be formed. Inaddition, a seed layer 734 has been formed over the first photoresistlayer 730. In some embodiments, the seed layer 734 can include titanium(Ti), copper (Cu), or any other suitable material. In some embodiments,the seed layer 734 can be formed via sputter deposition, or any othersuitable deposition method.

In FIG. 7C, a second photoresist layer 740 has been formed over thefirst photoresist layer 730 and the seed layer 734, and patterned viaphotolithography to form inner apertures 742 a and 742 b, as well as anouter aperture 744 extending around the IDT electrodes 720 and the innerapertures 742 a and 742 b. The inner apertures 742 a and 742 b overliethe stopper structures 728 a and 728 b, and are aligned with theapertures 732 a and 732 b in the first photoresist layer 730, but areslightly smaller, such that the seed layer 740 on the sidewalls of theapertures 732 a and 732 b are covered by portions of the secondphotoresist layer 740. The apertures 732 a and 732 b are depicted in theillustrated embodiment as having similar dimensions to the underlyingstopper structures 728 a and 728 b, but in other embodiments, thestopper structures 728 a and 728 b may be larger or smaller in somedimensions than the apertures 732 a and 732 b. The outer aperture 744will be used in part to define the locations of a package wall.

In FIG. 7D, additional structures have been formed within the outeraperture 744 and the inner apertures 742 a and 742 b, overlying thestopper structures 728 a and 728 b. An interconnect layer 722 has beenformed within inner aperture 742 a, overlying the stopper structure 728a. The interconnect layer 722 can be used to form a connection with theIDT electrodes 720, and may extend beyond the edge of the stopperstructure 728 a. A lower layer 726 a of an internal interconnect pillarhas been formed within inner aperture 742 b, overlying the stopperstructure 728 b. A lower wall layer 746 a has been formed within theouter aperture 744. In some embodiments, the interconnect layer 722, thelower layer 726 a of the internal interconnect pillar, and the lowerwall layer 746 a can be formed via an electroplating process or othersuitable process, and can include copper or another suitable material.

In the illustrated embodiment, a third photoresist layer 760 has beenformed over the second photoresist layer 740. The third photoresistlayer 760 has been patterned to form an aperture 762 exposing a sectionof the lower layer 726 a of the internal interconnect pillar, and toform an aperture 764 exposing a section of the lower wall layer 746 a.The third photoresist layer 760 extends over the interconnect layer 722without exposing a portion of the interconnect layer 722.

In FIG. 7E, a middle wall layer 746 b has been formed within theaperture 764 of the third photoresist layer 760, over the lower walllayer 746 a. A middle layer 726 b of the internal interconnect pillarhas been formed within the aperture 762 of the third photoresist layer760, over the lower layer 726 a of the internal interconnect pillar. Inthe illustrated embodiment, the middle wall layer 746 b and the middlelayer 726 b of the internal interconnect pillar are shown as extendingto roughly the height of the upper surface of the internal thirdphotoresist layer 760, but in other embodiments, the middle wall layer746 b and the middle layer 726 b of the internal interconnect pillar canextend to heights either above or below the upper surface of the thirdphotoresist layer 760.

In FIG. 7F, the partially fabricated resonator component has been beplanarized down to a desired height. This planarization process hasreduced the thickness of the third photoresist layer 760 as well as thethicknesses of the middle wall layer 746 b and the middle layer 726 b ofthe internal interconnect pillar. The middle wall layer 746 b and themiddle layer 726 b of the internal interconnect pillar still extend to aheight greater than the height of the interconnect layer 722, and aportion of the third photoresist layer 760 still extends over theinterconnect layer 722. By planarizing the third photoresist layer 760,the middle wall layer 746 b, and the middle layer 726 b of the internalinterconnect pillar to a desired height, the overall height of theresulting package can be reduced and/or minimized.

In FIG. 7G, an upper wall layer 746 c has been formed over the middlewall layer 746 b, and an upper layer 726 c of the internal interconnectpillar has been formed over the middle layer 726 b of the internalinterconnect pillar. In some embodiments, each of the middle and upperwall layers 746 b and 746 c, as well as the middle and upper layers 726b and 726 c of the internal interconnect pillar may be formed byelectroplating processes. In some embodiments, the middle layers mayinclude the same material as the lower layers, while the upper layersmay be a different material, such as tin (Sn) or a tin alloy, or anothersuitable material. Because the interconnect layer 722 remains covered bya section of the photoresist layer 760, no additional layer will beformed over the interconnect layer 722 during an electroplating process.

In FIG. 7H, the photoresist layers and seed layer have been removed toform a finished wafer which is ready for bonding to a second wafer toform a SAW resonator package. The wall layers form a wall 746 extendingaround the periphery of the SAW resonator on finished wafer. The wall746 has a height equal to the height of the internal interconnect pillar726. The interconnect layer 722 has a height which is less than theheight of the wall 746 and the internal interconnect pillar 726.

In FIG. 7I, a second SAW wafer 700 b has been bonded to the first SAWwafer 700 a to form a packaged acoustic wave component 702 (e.g., astacked SAW resonator package). In the illustrated embodiment, thesecond SAW wafer 700 b includes a piezoelectric layer 710 b having aplurality of IDT electrodes 720 b formed thereon. In addition, thesecond SAW wafer 700 b has bonding pads 748 a and 748 b correspondingrespectively to the position and locations of the wall 746 and theinternal interconnect pillar 726 of the first SAW wafer 700 a. In someembodiments, the bonding pads 748 include gold (Au) or a gold alloy, andcan be bonded to tin layers on the upper surface of the wall 746 and theinternal interconnect pillar 726. The bonding pad 748 b to which theinternal interconnect pillar 726 is bonded may be in electricalcommunication, via an interconnect or other suitable structure, with theIDT electrodes 720 b of the second SAW wafer 700 b.

After bonding the second SAW wafer 700 b to the first SAW wafer 700 a toform the packaged acoustic wave component 702, the lower surface of thefirst SAW wafer 700 a may be ground back to reduce the thickness of thepiezoelectric layer 710 a to a desired thickness. In the illustratedembodiment, the piezoelectric layer 710 a has been reduced to a smallerthickness than the thickness of the piezoelectric layer 710 b.

In FIG. 7J, the outer surface of the piezoelectric layer 710 a has beenexposed to illumination from an etching layer at least at two locations.The first location is on the opposite side of the stopper structure 728a (see FIG. 7D) at or near the base of the interconnect layer 722. Afirst laser-drilled via 780 a has been formed at this first location,stopping on the stopper structure underlying the interconnect layer 722to expose a portion of the stopper structure underlying interconnectlayer 722. The second location is on the opposite side of the stopperstructure 728 b (see FIG. 7D) at or near the base of the internalinterconnect pillar 726. A second laser-drilled via 780 b has beenformed at this location, stopping on the stopper structure of theinternal interconnect pillar 726. The laser-drilled vias 780 a and 780 bcan extend into the stopper structures of the interconnect layer 722 andthe internal interconnect pillar 726, without extending into theportions of the interconnect layer 722 and the internal interconnectpillar 726 overlying the stopper structures.

In FIG. 7K, after the formation of the laser-drilled vias 780 a and 780b, a seed layer 782 has been formed over at least a portion of the outersurface of the piezoelectric layer 710 a and coating the interiorsurfaces of the laser-drilled vias 780 a and 780 b and the exposedsections of the stopper structures. This seed layer 782 may be formed bysputter deposition or another suitable process.

In FIG. 7L, a photoresist layer 784 has been formed over the seed layer782, and patterned to form apertures exposing portions of the seed layer782 covering the interior of the vias 780 a and 780 b and immediatelyadjacent the vias 780 a and 780 b. The size of the apertures in thephotoresist layer 784 will define the size of the interconnectstructures which will be formed within the photoresist layer 784. Byexposing portions of the seed layer 782 adjacent the vias 780 a and 780b, the interconnect structures may be made larger than the vias 780 aand 780 b themselves.

In FIG. 7M, interconnect structures 786 a and 786 b have been formedover the exposed portion of the seed layer 782, within the aperturesformed in the photoresist layer 784. The interconnect structures 786 aand 786 b cover at least the respective vias 780 a and 780 b and theportions of the seed layer immediately surrounding the vias 780 a and780 b. The interconnect structures 786 a and 786 b may be formed, forexample, by electroplating onto the seed layer, or using any othersuitable fabrication process. In some embodiments, the lower surfaces ofthe interconnect structures may be planarized after the electroplatingprocess. The interconnect structures 786 a and 786 b may include copperor other suitable conductive materials. The interconnect structure 786 aand 786 b can include a conductive materials 788 a and 788 b disposed inthe vias 780 a and 780 b, and the interconnect pillar 726.

In FIG. 7N, lower layers 789 a and 789 b have been added to interconnectstructures 786 a and 786 b. In such embodiments, the interconnectstructures 786 a and 786 b can include multiple layers of materials,such as a layer of copper adjacent the seed layer, followed by lowerlayers 789 a and 789 b including tin, formed on the exposed lowersurfaces of the interconnect structures. The formation of a lower layer789 a and 789 b on the exposed lower surfaces of the interconnectstructures 786 a and 786 b can facilitate bonding of the finishedpackages to other components.

In FIG. 7O, the photoresist layer 784 and the exposed portions of theseed layer have been removed, leaving the interconnect structures 786 aand 786 b. A packaged acoustic wave component 700 has been formed,including IDT electrodes 720 a and 720 b on facing piezoelectric layers710 a and 710 b. The interconnect structure 786 a extends into the via780 a, and is in electrical communication with the IDT electrodes 720 athrough the interconnect layer 722 on the opposite side of thepiezoelectric layer 710 a, allowing communication with the IDTelectrodes 720 a through the piezoelectric layer 710 a. The interconnectstructure 786 b extends into the via 780 b, and is in electricalcommunication with the IDT electrodes 720 b through the internalinterconnect pillar 726 on the opposite side of the piezoelectric layer710 a, allowing communication with the IDT electrodes 720 b through thesame piezoelectric layer 710 a, rather than through the piezoelectriclayer 710 b supporting the IDT electrodes 720 b.

FIG. 8 is a schematic diagram of an example transmit filter 800 thatincludes surface acoustic wave resonators of a surface acoustic wavecomponent according to an embodiment. The transmit filter 800 can be aband pass filter. The illustrated transmit filter 800 is arranged tofilter a radio frequency signal received at a transmit port TX andprovide a filtered output signal to an antenna port ANT. Some or all ofthe SAW resonators TS1 to TS7 and/or TP1 to TP5 can be SAW resonators incommunication with a conductive structure extending through alaser-drilled via in accordance with any suitable principles andadvantages disclosed herein. In addition, two or more of the SAWresonators of the transmit filter 800 can be in a stacked resonatorpackage such as the packaged acoustic wave component 700 of FIG. 7J.Alternatively or additionally, one or more of the SAW resonators of thetransmit filter 800 can be any surface acoustic wave resonator disclosedherein, or part of a stacked resonator package disclosed herein. Anysuitable number of series SAW resonators and shunt SAW resonators can beincluded in a transmit filter 800.

FIG. 9 is a schematic diagram of a receive filter 900 that includessurface acoustic wave resonators of a surface acoustic wave componentaccording to an embodiment. The receive filter 900 can be a band passfilter. The illustrated receive filter 900 is arranged to filter a radiofrequency signal received at an antenna port ANT and provide a filteredoutput signal to a receive port RX. Some or all of the SAW resonatorsRS1 to RS8 and/or RP1 to RP6 can be SAW resonators in communication witha conductive structure extending through a laser-drilled via inaccordance with any suitable principles and advantages disclosed herein.In addition, two or more of the SAW resonators of the receive filter 900can be in a stacked resonator package such as the packaged acoustic wavecomponent 700 of FIG. 7J. Alternatively or additionally, one or more ofthe SAW resonators of the receive filter 900 can be any surface acousticwave resonator disclosed herein, or part of a stacked resonator packagedisclosed herein. Any suitable number of series SAW resonators and shuntSAW resonators can be included in a receive filter 950.

FIG. 10 is a schematic diagram of a radio frequency module 1000 thatincludes a surface acoustic wave component 1076 according to anembodiment. The illustrated radio frequency module 1000 includes the SAWcomponent 1076 and other circuitry 1077. The SAW component 1076 caninclude one or more SAW resonators with any suitable combination offeatures of the SAW resonators disclosed herein. The SAW component 1076can include a SAW die that includes SAW resonators.

The SAW component 1076 shown in FIG. 10 includes a filter 1078 andterminals 1079A and 1079B. The filter 1078 includes SAW resonators. Oneor more of the SAW resonators can be SAW resonators in communicationwith a conductive structure extending through a laser-drilled via inaccordance with any suitable principles and advantages disclosed herein.In addition, two or more of the SAW resonators of the filter 1078 can bein a stacked resonator package such as the packaged acoustic wavecomponent 700 of FIG. 7J. The terminals 1079A and 1078B can serve, forexample, as an input contact and an output contact, and may be inelectrical communication with a conductive structure extending through alaser-drilled via. The SAW component 1076 and the other circuitry 1077are on or positioned over a common packaging substrate 1080 in FIG. 10 .The package substrate 1080 can be a laminate substrate. The terminals1079A and 1079B can be electrically connected to contacts 1081A and1081B, respectively, on or positioned over the packaging substrate 1080by way of electrical connectors 1082A and 1082B, respectively. Theelectrical connectors 1082A and 1082B can be bumps or wire bonds, forexample. The other circuitry 1077 can include any suitable additionalcircuitry. For example, the other circuitry can include one or more oneor more power amplifiers, one or more radio frequency switches, one ormore additional filters, one or more low noise amplifiers, the like, orany suitable combination thereof. The radio frequency module 1000 caninclude one or more packaging structures to, for example, provideprotection and/or facilitate easier handling of the radio frequencymodule 1000. Such a packaging structure can include an overmoldstructure formed over the packaging substrate 1080. The overmoldstructure can encapsulate some or all of the components of the radiofrequency module 1000.

FIG. 11 is a schematic diagram of a radio frequency module 1100 thatincludes a surface acoustic wave component according to an embodiment.As illustrated, the radio frequency module 1100 includes duplexers 1185Ato 1185N that include respective transmit filters 1186A1 to 1186N1 andrespective receive filters 1186A2 to 1186N2, a power amplifier 1187, aselect switch 1188, and an antenna switch 1189. The radio frequencymodule 1100 can include a package that encloses the illustratedelements. The illustrated elements can be disposed on a common packagingsubstrate 1180. The packaging substrate can be a laminate substrate, forexample.

The duplexers 1185A to 1185N can each include two acoustic wave filterscoupled to a common node. The two acoustic wave filters can be atransmit filter and a receive filter. As illustrated, the transmitfilter and the receive filter can each be band pass filters arranged tofilter a radio frequency signal. One or more of the transmit filters1186A1 to 1186N1 can include one or more SAW resonators in accordancewith any suitable principles and advantages disclosed herein. Similarly,one or more of the receive filters 1186A2 to 1186N2 can include one ormore SAW resonators in accordance with any suitable principles andadvantages disclosed herein. Although FIG. 12 illustrates duplexers, anysuitable principles and advantages disclosed herein can be implementedin other multiplexers (e.g., quadplexers, hexaplexers, octoplexers,etc.) and/or in switch-plexers.

The power amplifier 1187 can amplify a radio frequency signal. Theillustrated switch 1188 is a multi-throw radio frequency switch. Theswitch 1188 can electrically couple an output of the power amplifier1187 to a selected transmit filter of the transmit filters 1186A1 to1186N1. In some instances, the switch 1188 can electrically connect theoutput of the power amplifier 1187 to more than one of the transmitfilters 1186A1 to 1186N1. The antenna switch 1189 can selectively couplea signal from one or more of the duplexers 1185A to 1185N to an antennaport ANT. The duplexers 1185A to 1185N can be associated with differentfrequency bands and/or different modes of operation (e.g., differentpower modes, different signaling modes, etc.).

FIG. 12 is a schematic block diagram of a module 1210 that includes apower amplifier 1292, a radio frequency switch 1293, and duplexers 1291Ato 1291N in accordance with one or more embodiments. The power amplifier1292 can amplify a radio frequency signal. The radio frequency switch1293 can be a multi-throw radio frequency switch. The radio frequencyswitch 1293 can electrically couple an output of the power amplifier1292 to a selected transmit filter of the duplexers 1291A to 1291N. Oneor more filters of the duplexers 1291A to 1291N can include any suitablenumber of surface acoustic wave resonators in communication with aconductive structure extending through a laser-drilled via, or as partof a stacked resonator package, in accordance with any suitableprinciples and advantages discussed herein. Any suitable number ofduplexers 1291A to 1291N can be implemented.

FIG. 13 is a schematic block diagram of a module 1395 that includesduplexers 1391A to 1391N and an antenna switch 1394. One or more filtersof the duplexers 1391A to 1391N can include any suitable number ofsurface acoustic wave resonators in communication with a conductivestructure extending through a laser-drilled via, or as part of a stackedresonator package, in accordance with any suitable principles andadvantages discussed herein. Any suitable number of duplexers 1391A to1391N can be implemented. The antenna switch 1394 can have a number ofthrows corresponding to the number of duplexers 1391A to 1391N. Theantenna switch 1394 can electrically couple a selected duplexer to anantenna port of the module 1395.

FIG. 14 is a schematic diagram of a wireless communication device 1400that includes filters 1403 in a radio frequency front end 1402 accordingto an embodiment. The filters 1403 can include one or more SAWresonators in accordance with any suitable principles and advantagesdiscussed herein. The wireless communication device 1400 can be anysuitable wireless communication device. For instance, a wirelesscommunication device 1400 can be a mobile phone, such as a smart phone.As illustrated, the wireless communication device 1400 includes anantenna 1401, an RF front end 1402, a transceiver 1404, a processor1405, a memory 1406, and a user interface 1407. The antenna 1401 cantransmit RF signals provided by the RF front end 1402. Such RF signalscan include carrier aggregation signals. Although not illustrated, thewireless communication device 1400 can include a microphone and aspeaker in certain applications.

The RF front end 1402 can include one or more power amplifiers, one ormore low noise amplifiers, one or more RF switches, one or more receivefilters, one or more transmit filters, one or more duplex filters, oneor more multiplexers, one or more frequency multiplexing circuits, thelike, or any suitable combination thereof. The RF front end 1402 cantransmit and receive RF signals associated with any suitablecommunication standards. The filters 1403 can include SAW resonators ofa SAW component that includes any suitable combination of featuresdiscussed with reference to any embodiments discussed above.

The transceiver 1404 can provide RF signals to the RF front end 1402 foramplification and/or other processing. The transceiver 1404 can alsoprocess an RF signal provided by a low noise amplifier of the RF frontend 1402. The transceiver 1404 is in communication with the processor1405. The processor 1405 can be a baseband processor. The processor 1405can provide any suitable base band processing functions for the wirelesscommunication device 1400. The memory 1406 can be accessed by theprocessor 1405. The memory 1406 can store any suitable data for thewireless communication device 1400. The user interface 1407 can be anysuitable user interface, such as a display with touch screencapabilities.

FIG. 15 is a schematic diagram of a wireless communication device 1510that includes filters 1503 in a radio frequency front end 1502 andsecond filters 1513 in a diversity receive module 1512. The wirelesscommunication device 1510 is like the wireless communication device 1500of FIG. 14 , except that the wireless communication device 1520 alsoincludes diversity receive features. As illustrated in FIG. 15 , thewireless communication device 1520 includes a diversity antenna 1511, adiversity module 1512 configured to process signals received by thediversity antenna 1511 and including filters 1513, and a transceiver1504 in communication with both the radio frequency front end 1502 andthe diversity receive module 1512. The filters 1513 can include one ormore SAW resonators that include any suitable combination of featuresdiscussed with reference to any embodiments discussed above.

Although embodiments disclosed herein relate to surface acoustic waveresonators, any suitable principles and advantages disclosed herein canbe applied to other types of acoustic wave resonators, such as Lamb waveresonators and/or boundary wave resonators. For example, any resonatorincluding a substrate suitable for etching by lasers can have alaser-drilled via formed therethrough, using a stopper layer or stopperstructure which is highly reflective to the wavelength of the etchinglaser. These vias can be used to provide communication with theresonator into a package enclosing the resonator, where the substratethrough which the via is laser-drilled is used to form part of thepackage enclosing the resonator.

Any of the embodiments described above can be implemented in associationwith mobile devices such as cellular handsets. The principles andadvantages of the embodiments can be used for any systems or apparatus,such as any uplink wireless communication device, that could benefitfrom any of the embodiments described herein. The teachings herein areapplicable to a variety of systems. Although this disclosure includessome example embodiments, the teachings described herein can be appliedto a variety of structures. Any of the principles and advantagesdiscussed herein can be implemented in association with RF circuitsconfigured to process signals in a frequency range from about 30 kHz to300 GHz, such as in a frequency range from about 450 MHz to 8.5 GHz.

An acoustic wave resonator including any suitable combination offeatures disclosed herein can be included in a filter arranged to filtera radio frequency signal in a fifth generation (5G) New Radio (NR)operating band within Frequency Range 1 (FR1). A filter arranged tofilter a radio frequency signal in a 5G NR operating band can includeone or more acoustic wave resonators disclosed herein. FR1 can be from410 MHz to 7.125 GHz, for example, as specified in a current 5G NRspecification. One or more acoustic wave resonators in accordance withany suitable principles and advantages disclosed herein can be includedin a filter arranged to filter a radio frequency signal in a fourthgeneration (4G) Long Term Evolution (LTE) operating band and/or in afilter with a passband that spans a 4G LTE operating band and a 5G NRoperating band.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as die and/or acoustic wave components and/oracoustic wave filter assemblies and/or packaged radio frequency modules,uplink wireless communication devices, wireless communicationinfrastructure, electronic test equipment, etc. Examples of theelectronic devices can include, but are not limited to, a mobile phonesuch as a smart phone, a wearable computing device such as a smart watchor an ear piece, a telephone, a television, a computer monitor, acomputer, a modem, a hand-held computer, a laptop computer, a tabletcomputer, a personal digital assistant (PDA), a microwave, arefrigerator, an automobile, a stereo system, a DVD player, a CD player,a digital music player such as an MP3 player, a radio, a camcorder, acamera, a digital camera, a portable memory chip, a washer, a dryer, awasher/dryer, a copier, a facsimile machine, a scanner, amulti-functional peripheral device, a wrist watch, a clock, etc.Further, the electronic devices can include unfinished products.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,”“include,” “including” and the like are to be construed in an inclusivesense, as opposed to an exclusive or exhaustive sense; that is to say,in the sense of “including, but not limited to.” The word “coupled”, asgenerally used herein, refers to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Likewise, the word “connected”, as generally used herein,refers to two or more elements that may be either directly connected, orconnected by way of one or more intermediate elements. Additionally, thewords “herein,” “above,” “below,” and words of similar import, when usedin this application, shall refer to this application as a whole and notto any particular portions of this application. Where the contextpermits, words in the above Detailed Description using the singular orplural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel apparatus, methods, andsystems described herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the disclosure. For example, while blocks arepresented in a given arrangement, alternative embodiments may performsimilar functionalities with different components and/or circuittopologies, and some blocks may be deleted, moved, added, subdivided,combined, and/or modified. Each of these blocks may be implemented in avariety of different ways. Any suitable combination of the elements andacts of the various embodiments described above can be combined toprovide further embodiments. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the disclosure.

What is claimed is:
 1. A packaged acoustic wave component comprising: afirst acoustic wave resonator including a first interdigital transducerelectrode positioned over a first piezoelectric layer; a second acousticwave resonator including a second interdigital transducer electrodepositioned over a second piezoelectric layer, the second piezoelectriclayer being bonded to the first piezoelectric layer; and a stopperstructure positioned over the first piezoelectric layer, the stopperstructure positioned above a via extending through the firstpiezoelectric layer, the stopper structure in electrical communicationwith the first interdigital transducer electrode and including amaterial which reflects at least fifty percent of light having awavelength of 355 nanometers, the via being a laser drilled via; thelaser-drilled via further extends at least partially through the stopperstructure.
 2. The packaged acoustic wave component of claim 1 furthercomprising a second stopper structure positioned over the firstpiezoelectric layer, the second stopper structure positioned over asecond laser-drilled via extending through the first piezoelectriclayer, the second stopper structure in electrical communication with thesecond interdigital transducer electrode.
 3. The packaged acoustic wavecomponent of claim 2 wherein the second stopper structure includes amaterial which reflects at least fifty percent of light having awavelength of 355 nanometers.
 4. The packaged acoustic wave component ofclaim 2 further comprising an interconnect layer in electricalcommunication with the first interdigital transducer electrode and thestopper structure, the interconnect layer positioned over at least aportion of the stopper structure.
 5. The packaged acoustic wavecomponent of claim 2 further comprising an interconnect structureextending between the first piezoelectric layer and the secondpiezoelectric layer, the interconnect structure in electricalcommunication with the second interdigital transducer electrode and thesecond stopper structure, wherein the interconnect structure ispositioned over at least a portion of the second stopper structure. 6.The packaged acoustic wave component of claim 2 further comprising awall surrounding a region including the first and second acoustic waveresonators, the wall bonding the first piezoelectric layer to the secondpiezoelectric layer to form a package structure, wherein at least one ofthe stopper structure or the second stopper structure is located withinthe region surrounded by the wall.
 7. The packaged acoustic wavecomponent of claim 2 wherein at least one of the stopper structure orsecond stopper structure includes a material which reflects at leastseventy-five percent reflective of light having a wavelength of 355nanometers.
 8. The packaged acoustic wave component of claim 2 whereinat least one of the stopper structure or second stopper structure is analuminum layer.
 9. The packaged acoustic wave component of claim 2wherein at least one of the stopper structure or second stopperstructure has a thickness of less than 5 micrometers.
 10. The packagedacoustic wave component of claim 1 wherein the first and secondpiezoelectric layers are lithium tantalate layers, or lithium niobatelayers.
 11. A packaged acoustic wave component comprising: a firstacoustic wave resonator including a first interdigital transducerelectrode positioned over a first piezoelectric layer; a second acousticwave resonator including a second interdigital transducer electrodepositioned over a second piezoelectric layer, the second piezoelectriclayer being bonded to the first piezoelectric to form a packageencapsulating the first and second interdigital transducer electrodes;and a stopper structure positioned over the first piezoelectric layer,the stopper structure positioned over a via extending through the firstpiezoelectric layer, the stopper structure including aluminum, thestopper structure having an ablated or melted portion on a side of thestopper structure that faces the via.
 12. The packaged acoustic wavecomponent of claim 11 wherein the via is a laser-drilled via.
 13. Thepackaged acoustic wave component of claim 11 further comprising a firstconductive structure extending into the via, the first conductivestructure in electrical communication with the first interdigitaltransducer electrode.
 14. The packaged acoustic wave component of claim11 further comprising a second stopper structure positioned over thefirst piezoelectric layer, the second stopper structure positioned overa second laser-drilled via extending through the first piezoelectriclayer, the stopper structure and second stopper structure includingaluminum.
 15. The packaged acoustic wave component of claim 14 furthercomprising a second conductive structure extending into the second via,the second conductive structure in electrical communication with thesecond interdigital transducer electrode.
 16. The packaged acoustic wavecomponent of claim 11 further comprising an interconnect layer inelectrical communication with the first interdigital transducerelectrode and the stopper structure, the interconnect layer positionedover at least a portion of the stopper structure.
 17. The packagedacoustic wave component of claim 11 wherein the stopper structure has athickness of less than 5 micrometers.
 18. The packaged acoustic wavecomponent of claim 11 wherein an overall thickness of the package isless than 200 micrometers.
 19. The packaged acoustic wave component ofclaim 11 wherein the first acoustic wave resonator is associated with afirst frequency band, and the second acoustic wave resonator isassociated with a second frequency band, wherein the first frequencyband is different than the second frequency band.